The invention relates to a device for vertically displacing a lower roll of a pair of rolls, running on bearings in a roll stand, for adjusting the upper side of that roll to the rolling line, wherein the rolls run on bearings in chocks and optionally can be supported by supporting rolls likewise running on bearings in chocks, which device comprises actuators having supporting surfaces and having mating supporting surfaces arranged at different height levels in the direction of displacement, which selectively may be brought into and out of contact with the supporting surfaces, which actuators are built in between the chocks of the lower roll and/or the chocks of the lower supporting roll and the roll stand.
A device of this kind is known for example from DE-A-1 33 31 479 and from DE-A-1 38 26 544.
According to the latter document, the actuator has a rotary disk, which acts on a pressure disk, wherein, depending on the torsion of the rotary disk, circular-ring segment surfaces provided on the rotary disk come to sit adjacent to circular-ring segment surfaces of the pressure disk or between them. Thereby, however, only two heights of adjustment for screwing down a roll to the rolling line are possible. For deviating heights of adjustment, the actuators would have to be changed.
According to DE-A-1 33 31 479, each actuator is constituted by a supporting component having a pair of fitting plates having two supporting surfaces and by an adjusting disk having mating supporting surfaces arranged at different heights and designed in the form of circular-ring segments, which adjusting disk runs on bearings on the roll stand, being pivotable against the supporting component. The two supporting surfaces of the supporting component sit adjacent to the mating supporting surfaces arranged on the pivotable adjusting disk, adjacent mating supporting surfaces being provided at different heights and mating supporting surfaces opposed in pairs being provided at the same height. Since the supporting surface must have a certain mimimum size to ensure a surface pressure being lower than the maximum admissible surface pressure, the mating supporting surfaces must also have a corresponding size, so that only few mating supporting surfaces sitting at different height levels are feasible. From this results a device which allows only few possibilities of adjustment. In order to ensure a considerable total height of adjustment all the same, only a very coarse adjustment of a roll to the rolling line is possible, i.e., the height graduations from mating supporting surface to mating supporting surface must be, on account of the small number of the same, relatively large to achieve a required minimum total height of adjustment.
The invention aims at avoiding these disadvantages and difficulties and has as its object to provide a device of the initially described kind, which allows, on the one hand, to ensure a considerable total height of adjustment and, on the other hand, to achieve a height adjustment of a roll to the rolling line which is as fine as possible. Here, particularly a very low specific surface pressure which is far below the maximum admissible surface pressure should be feasible.
According to the invention, this object is achieved in that each actuator comprises two bushes which are relatively twistable against each other around an axis oriented in the direction of displacement and which can be brought into and out of contact in the direction of the axis, one bush having the supporting surfaces and the second bush having mating supporting surfaces designed diametrically opposed to the supporting surfaces.
Preferably, one of the bushes is not twistable against the roll stand, and the second bush is twistable against the other bush and/or against the roll stand.
To be able to twist the bushes relatively to each other in a simple way even when the supporting surfaces and mating supporting surfaces are arranged in steps, suitably one of the bushes can be, by means of a pressure-medium cylinder, elevated and lowered against the other bush in the direction of displacement; preferably, the bush which is not twistable against the roll stand can be elevated and lowered, whereas the bush which is twistable against the roll stand is, with regard to height, fixed relative to the roll stand, and, furthermore, a pressure-medium cylinder arranged centrally in the corresponding second bush is provided for elevating and lowering a bush.
Suitably, both the supporting surfaces and the mating supporting surfaces are arranged in a helical form and make up a thread extending over 360xc2x0 . Here, the thread is divided into two sections having each an angle at circumference of 180xc2x0, so that the maximum height of adjustment is half of the lead.
A preferred embodiment is characterized in that the supporting surfaces and mating supporting surfaces are arranged in a helical form and are designed as extending two times over an angle at circumference of 180xc2x0, respectively, and thus form half a thread, respectively, wherein both half threads sit at the same height, which ensures a symmetrical load on both bushes in each of their positions.
For smaller relative torsions of the bushes against each other it is suitable if the twistable bush is pivotable by means of a pressure-medium cylinder supported by the roll stand on the one hand and the bush on the other hand.
For bigger angles of torsion of the bushes against each other it is suitable if the pivotable bush on its circumferential side is provided with an annular-gear segment in which a pinion motor engages.
A particularly preferred embodiment is characterized in that the pivotable bush is provided with an annular-gear segment on its circumferential side and that a toothed rack, which is movable in the longitudinal direction by means of a pressure-medium cylinder, can be engaged in and/or disengaged from the annular-gear segment.
Preferably, the supporting surfaces and mating supporting surfaces are constituted by element surfaces which are arranged staggered with regard to height in the form of a winding staircase, the element surfaces advantageously being oriented vertically to the rotation axis of the bushes.
However, it is also possible to arrange the element surfaces as being inclined relative to the rotation axis of the bushes.
To achieve a bearing area of the supporting surfaces and mating supporting surfaces which is as large as possible, the element surfaces are designed in the form of circular-ring segments.
Another preferred embodiment is characterized in that the supporting surfaces and mating supporting surfaces are constituted by surfaces forming identical teeth, respectively, wherein the teeth of both the supporting surface and the mating supporting surface are arranged along a screw-shaped surface having the same gradient and can be engaged under formation of a gear-tooth system, and wherein the gear-tooth system is advantageously designed as a serration. When the gear-tooth system has a fine design, the present embodiment makes it possible to achieve a very fine height adjustment of the roll to the rolling line.
To achieve the possibility of continuous adjustment of the roll to the rolling line, suitably the supporting surfaces and mating supporting surfaces are designed as screw-shaped sliding surfaces, respectively, which have the same gradient, the angle of inclination being smaller than the corresponding angle of friction.
Advantageously, a torsion lock against unintended relative twisting of the two bushes is provided here in addition to the supporting surfaces and mating supporting surfaces, preferably formed by teeth on one of the bushes, which engage in counter-teeth on the second bush, which corresponds to said bush, the teeth being provided on the side of the outer circumference of the bushes.
The invention further comprises a roll stand with two working rolls, which is equipped with an inventive device for vertically displacing rolls running on bearings in a roll stand, for adjusting the upper edge of the lower roll of a pair of rolls to the rolling line. That roll stand suitably has working rolls which can be supported by supporting rolls.